darknessph

(unexpectedly cracked rotor - Centric Premium High Carbon. OE rotor lasts much longer)


The Renault Rotor mockup


Would you believe that the two are the same diameter? damn.
The reanult rotor is designed to take larger pads
(note the rotor hat attachment to either front / rear ring)


Renault rotor thickness


Thickness of the said cracked rotor


Rotor vane comparison
Renault rotor has odd design attaching the front ring to the front.
Instead of one long vane, it is split up into three section, kinda offset.
This may not be optimal for cooling though



Notice the holes in the hat. Have seen this in some older Lotus vehicles.


The micropores in question

Hello yall!

Well Well, after cracking the two sets of new front rotors since last September, I've run out of front rotors. Of course, a rotor cracks a couple days before a track day just street driving out of blue.

Out of some thirty rotors for other cars compared against OEM S2000 rotor, I came across a Renault-Samsung Sm5 (Renault laguna / Safrane) rotor that is particular in its design. It is kinda like a two-piece rotor in that it can keep the heat away from the wheel bearings by utilizing reduced material around where the rotor hat attaches to the rotor ring. It is thicker, five pounds heavier, but it also means that its thermal capacity is going to be higher too. Thermal capacity of the stock S2000 brake is inadequate S2000's weight and power) The hat is attached to the rear portion of the ring, which is unlike that of S2000 (front ring attached the hat).

After some fiddling with backing plate, machining out the center bore to 70.1mm, etc it fit perfectly. Yay for $100 brake upgrade! (well, at least in the thermal capacity and durability aspects..)

But after the drive home from work, I've noticed that there are micropores on the rotor surface. I know as far as that these are minor casting defects called porosites. However, I've never seen these holes on a brake rotor though.

What do you say? could it contribute to early rotor crack / failure and should I do myself away from these rotors or would it be fine?

edit: added pics

gptoyz

While I applaud the effort to find a cure to rotor cracking, I don't think that rotor will be a good upgrade for tracking or high performance rotors.

First off, what I have learned so far is that factory rotors have pretty good metallurgy, certainly better than most of the aftermarket s2000 fitment rotors. This is what I have found to be the most durable under track conditions:
Project Mu Club Racer > APM J Hook > Honda OEM > Autozone Duralast > Centric Premium > Centric Standard/Ctek

Cost wise I rank them as such:
Centric Standard/Ctek < Autozone Duralast = Centric Premium < APM J Hook = Honda OEM < Project Mu Club Racer

The problems I see with the renault rotor are:
Vane Design
Weight

First thing that concerns me is that the s2000 front rotor already doesn't have enough cooling across the oem vane design to pump the air from the center outwards. With the renault rotor that design becomes even more impacted because the vanes aren't even opened to clean air it looks like the vanes would be sealed up against the hub or at least air flow severely impacted

Another thing, you are adding 10 lbs of spinning unsprung gyroscopic weight - that's like counter intuitive and counter productive to producing a faster car.

Going back to my original find, rotor cracking seems to more prevalent with bad construction and bad metals more than anything.

darknessph

Good call. I have used similar rotors as you have and found similar results.

Autozone Duralast Blanks - Lasts about 4 track days
Autozone Drilled & Slotted ones - Lasted two sessions lol (Multiple cracks in the pit, cooling)(Was on the car when I bought the car, I only buy blanks)
Centric Premium blanks - Lasts 2-3 track days
OEM rotors - Used two sets- both lasted more than 5 track days and lots of street, autocross miles

After a track day with the Renault rotors, it is doing pretty well. Five sessions on a brake-intensive course barely left a mark on the rotor surface (no crazing yet) when it would've showed up on OE rotors by now.



There is indeed a notable increase in the unsprung mass by about five pounds, but considering the rotor's availability in this country and the cost, I'd say it performs pretty well. It does lower the hub temperature considerably (now around 200-300F measured in the hot pits) and the rotor temps are lower by 100-200F. This is without any cooling mods.

Once I get my hands on a set of OE rotors again, I'll switch to it and see how long it lasts in comparison to the Renault rotors.



(Time for brake cooling before anything though)

darknessph

Surprise...!

Check this out:

http://www.gotuning.com/product_info...roducts_id=864



Looks like this reverse-config disc design is new paradigm

billios996

so the rotor is drawing in air from the front face at the hub and blowing radially outward for cooling on these rather than drawing from the perimeter and blowing out the backside hub?

Were you able to use the stock size calipers and brake pads with the extra thickness rotor?

gptoyz

No what he means is that the vents draw air from the outward half of the rotor vs drawing the air from inner side of the rotor

It's a nice gimmick hasn't resulted in significant brake pad life


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